Apparatus for burning wood refuse



Dec. 17,1957 E. T. .ooueLAss, JR 2,816,694 r APPARATUS FOR-BURNING woon REFUSE Filed July so, 1954 2 Sheets-Sh eet 1 q 7 J4 an m N NV B H Q 5 N INVENTOR EDWARD z oouams m.

ATTORNEYS Dec. 17, 1957 E. T. DOUGLASS, JR 2,816,694

APPARATUS FOR BURNING woon REFUSE Filed July 30, 1954 2 Sheets-Sheet 2 INVENTOR Uniwd ates Patent '6 APPARATUS FOR BURNING WOOD REFUSE Edward T. Douglass, Jr., Birmingham, Ala.

Application July 30, 1954, Serial Np. 446,770

4 Cl im (Cl. ZZZ- 4 My invention relates to apparatus for'feeding sawdust, wood shavings and the like to boiler furnaces, and has for an object the provision of apparatus efiective to feed such material in a constant, even flow and in such manner as to insure complete combustion thereof.

' My invention contemplates feed apparatus in which the material is delivered to a rotating feeder and moves from that apparatus by gravity down a trough or chute where it cascades into the path of a high velocity blast of air issuing from a nozzle whereby the falling stream of material is entrained bythe air stream and blown into the combustion chamber of the furnace.

A more specific object is to provide a rotary feeder especially adapted for use in feeding sawdust, wood shavings and the like to the nozzle of my improved apparatus, which feeder comprises a rotating drum having secured on the surface thereof a plurality of radial vanes or blades which extend at an angle to the longitudinal center line of the drum, whereby as the drum rotates the material discharges in a continuous, even stream, which stream cascades downwardly to be struck by the before mentioned air stream.

In the burning of finely divided materials such as sawdust and wood shavings, difficulty has been experienced in obtaining even, complete combustion. As is known, sawdust from green timber contains from 40% to 60% water, depending upon the type of tree and the time of year it is felled. When such finely divided, high moisture content wood is blown into a furnace and allowed to pile on the fire bed, only the outer layer thereof is dried sufliciently to burn properly, leaving a core or inner layer of wet material. This condition creates a blanket which hinders combustion and which tends to smother the fire. Also, in shavings from kiln dried lumber the above described condition may exist. Since wood is quite hyd-roscopic, shavings from lumber containing as little as 10% moisture, in a very few minutes, under average atmospheric humidity conditions, will absorb considerably more moisture. By the time such shavings reach the combustion chamber the moisture content may have increased to as much as 20%.

Briefly, I overcome the above mentioned difficulties by cascading the wood material in an even,'relat ively thin stream in front of an air nozzle which blows the material against the hot fire wall of the furnace. During its passage into the furnace the sawdust or shavings is suspended in the air stream and in this loose state the heat in the furnace flashes the moisture in the wood into steam. Some of thefine particles burn completely while in suspension and those that fall upon the fire bed are substantially moisture free and hence burn evenly and completely. My invention thus is characterized by the absence of gob feeding, resulting in improved combustion.

Apparatus embodying features of my invention is illust'rated in the accompanying drawings forming a part of this application in which:

Fig. l is a somewhat diagrammatic view, partly broken away and in section, andshowing a two-boiler furnace 2 plant being supplied with wood waste from a collection chamber, the wood waste being fed to the fire boxes through my improved rotary feed means and blown thereinto by my improved nozzle;

Fig. 2 is an enlarged detail sectional view taken generally alongiline lI -I I of Fig. 1

'Fig. 3 is a detail sectional view taken generally along line III-Ill of Fig. 2; V

ig, 4 is a rag e ta detail p n i o a por ion of t e pp ough an o of mymp o e mtar ders, the view being taken generally along line I V-'IV of Fig. 2;

Fig. 5 i n ar e il ect ona e h ou h my p o d ot ry e d and,

Fig. 6 is a detail sectional view taken generally along line VI-VI of Fig. 5. I i

Referring now to the drawings for a better understanding of my invention 1 show in Fig. l, in almost wholly diagrammatic manner, a sawdust or wood waste feed system supplying the boiler fnmaces indicated at 10 and 10a. The wood waste in the form of sawdust or shavings, which hereafter in this specification and claims for the sake of description will sometimes be designated as sawdust, is supplied from the saw mill or the planing mill, as the case may be, through a pipe 11 which enters the upper end of a cyclone separator indicated generally by the numeral 12. The separator 12 may be supported on top of .a storage bin or house 13 A conveyor trough 14 passes beneath the open lower end of the bin 13. Inside the. trough is a dragtype chain conveyor shown at 16 in Fig. 4. The chain 16 maybe driven by an electric motor 17 through a chain drive 18 or the like, the chain 16 returning in the manner well understood for such devices.

As shown in Fig. l the overflow from the end of the trough farthest from the bin 13 may be caught by ,a down coming trough '19. A blower 21, driven by any suitable means, not shown, conveys the. overflow through a conduit 22 back to the upper end of the cyclone separator where the material is redeposited into a bin 13.

Adjacent each of the boiler furnaces the trough .14 may have an opening 23 therein to which is connected a down-coming chute 24. Sawdust thus conveyed into. trough 14 falls through the openings .23., lHtOthB chutes 24 and thence to my improved feeder 26. I

Inasmuch as the feeders 26 are identical ,in construc-. tion a description of one will suflice for both. As best shown in the detail drawings Figs. 2, 5 and 6, my improved rotary feeder comprises a shaft 27 which is mounted for rotation in bearings 28. Mounted on the shaft 27 is a drum 33 having closed end platessecured nonrotatably to the shaft 27. The bearings 28 are supported in any suitable manner from the end walls 29 of the housing. The housing has a fixed lower curved side wall 31. The upper edge of the opposite curved side wall 32 is provided with an outwardly extending portion 30 which is hinged at its outer edge at 33 to the housing. The lower edge of the curved side wall 32 rests against the housing and has mounted thereon a weight34. It will be seen from Fig. 5 that the lower edge of the section 32 is forward of a vertical plane passing through the hinge 33 whereby it is held in seated or closed position against the lower portion 25 of the housing by gravity. Mounted on the upper end of the curved section 32 and extending inwardly of the housing a plate 35 which is held in place by bolts 36 which pass through slotted holes 37 in the housing whereby the position of the plate is adjustable.

Secured to the surface of the drum 38 and spaced apart thereon are vanes or blades indicated by the numeral- 41. The blades have their longitudinal axes disposed at an angle to the longitudinal axis ofrthe drum 38' to provide an inclined mounting of the blades. The blades preferably are formed of rectangular lengths of plate which are rounded out along their inner edges 41a which contact the surface of drum 38 whereby the edges 41a.

may be welded to the surface of the drum. This provides blades 41 with straight outer edges 41b which rotate in close proximity to the inner edge of the plate 35 as shown in Fig. 5. The blades thus are fiat and unwarped throughout their entire lengths. The shaft 27 and hence the entire rotary portion ofmy improved feeder may be driven by an electric motor 42 through a chain 43 or the like as shown diagrammatically in the drawings. The motor may conveniently be supported on a bracket 44 alongside the down coming chute 46 which presently will be described more in detail.

From what has already been said it will be apparent that wood waste fed through the chute 24 to the intake side of my improved rotary feeder 26 is discharged therefrom as the drum 38 rotates. Due to the angular relationship of the blades 41 relative to the longitudinal axis of the drum, it will be seen that as the drum rotates the blades cause an even, gravity feeding of the material from the rotary feeder. Thus, instead of having the blades straight across which would result in feeding gobs of the material as the drum rotates, I have slanted the blades so that an even, cascading, uniform feed takes place as the drum rotates. Should a large piece of'wood waste pass into the feeder 26 it wedges between a blade 41 and the plate 35 which causes the section 32 to swing about its hinge 33 and open wide thus freeing the piece. When the piece is freed the section 32 falls by gravity to the closed position jarring the feeder and loosening material in the hopper. Also, the acting of the blades 41 relative to the plate 35 provides a chopping action which either severs or disengages the obstruction.

As stated, the chute 46 connects to the discharge side of the feeder 26 and the material discharged therefrom fiows by gravity as indicated in Fig. 2 of the drawing. At the lower end of the chute 46 I provide an open housing 47 into the open end of which the chute 46 discharges. The housing may be provided with a sloping bottom section 47a terminating in a feed opening 45. The bottom 47a is hinged at 40 whereby it may be raised or lowered as becomes necessary.

Disposed beneath the housing 47 in position to receive fuel therefrom is my improved feed nozzle 48. As shown in Fig. 3, the nozzle is generally rectangular in shape, of a width substantially that of the housing 47. It is provided with a relatively wide flat bottom 48:: and upstanding side walls 50 which are low in relation to the width of the bottom and which converge rearwardly as shown in dotted lines at 150 in Fig. 3. The rear wall is shown at 151 and joins the converging side walls 150. A cover plate 53 is joined to the rear wall 151 and to the side walls 50 and 150 and extends forwardly and downwardly, terminating in closely spaced relation to the bottom 48a. The space defined by the plate 53 together with the walls and bottom of the nozzle thus forms a plenum chamber for the supply of air through the restricted passage 54 formed by the plate 53 with the bottom 48a of the nozzle.

The plate 53, as shown in Fig. 3, stops short of the forward end of the nozzle so that the wood refuse being fed from the housing 47 falls onto the bottom 48a of the nozzle in front of the forward edge of the plate. Also, as shown in Figs. 2 and 3 the sloping bottom 47a of the housing 47 overhangs the nozzle. By reason of the hinge 40 in the bottom 47a the nozzle 48 can be raised and lowered to vary the angle of feed into the furnace.

Connected to the rear wall 151 of the nobble 48 is a pipe 49 through which a high velocity stream of air is supplied to the nozzle from a blower 51, driven by a motor 52. In operation wood refuse falls onto the nozzle 48 in front of the edge of the plate 53. The sawdust there is entrained by the high velocity air stream and is blown into'the combustion chamber of the furnace.

From the foregoing the operation of my improved apparatus may now be readily understood. With the chain 16 supplying wood waste from the storage bin 13, with the drum 38 rotating and with air being supplied from the nozzle 48, it will be seen that the wood waste is fed in an even stream into the chute 46. The wood waste cascades through the housing 47, onto the bottom section of the nozzle 48, in front of the plate 53 into the path of the high velocity air stream coming from beneath the plate. This high velocity air stream entrains the material and blows it into the furnace where the contained moisture is flashed into steam which passes out with the gases of combustion. The sawdust thus is ready to burn and does in fact burn largely in suspension. The amount that falls upon the fire bed is preheated and is ready for combustion which takes place evenly and in an efiicient manner.

From the foregoing it will be apparent that I have devised an improved apparatus for feeding and burning wood waste and the like into a furnace. My invention is entirely practical and lends itself admirably for use in conjunction with automatic devices to feed the boiler furnaces responsive to demands for steam as determined by standard and well known devices. The inclined blades on my improved rotary feeder maintain at all times a constant, uniform gravity flow of the material into the chute 46 and this in turn is fed into the furnace in an even and continuous manner by the injecting nozzle 48.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

I. In apparatus for feeding wood waste, a rotary feeder comprising, a drum mounted for rotation and having spaced radial blades thereon defining feed pockets, a housing for the drum having end walls and curved side walls, one of said side walls being hinged at its upper end along a line laterally displaced from a vertical plane passing through the axis of the drum and with its lower end at rest outwardly of a vertical plane passing through said hinge, and a plate secured to said hinged side wall near the top and extending inwardly of the feeder with its inner edge in closely spaced relation to the outer edges of adjacent blades.

2. In apparatus for feeding wood waste, a rotary feeder comprising, a drum mounted for rotation and having spaced radial blades thereon defining feed pockets, a housing for the drum having end walls and curved side walls, one of said side walls being hinged at its upper end along a line laterally disposed from a vertical plane passing through the axis of the drum and with its lower end at rest outwardly of a vertical plane passing through said hinge, a weight on the lower portion of said hinged side wall, and a plate secured to said hinged side wall near the top and extending inwardly of the feeder with its inner edge in closely spaced relation to the outer edges of adjacent blades.

3. In a rotary feeder a housing embodying oppositely disposed curved walls, a feed chute, a delivery chute, a hinge pivotally mounting one of the walls to the feed chute, the lower edge of said pivotally mounted wall resting by gravity on the delivery chute along a line outwardly of a vertical plane passing through the hinge, a drum mounted in the housing, pocket forming vanes on the drum, and means to rotate the drum in a direction for the vanes to move toward the pivotally mounted wall during the upper part of their travel.

4. In a rotary feeder a housing embodying oppositely disposed curved walls, a feed chute, a delivery chute, a hinge pivotally mounting one of the walls to the feed chute, the. lower edge of said pivotally mounted wall rest-..

References Cited in the file of this patent UNITED STATES PATENTS 187,536 Kimball Feb. 20, 1877 6 Palmer Apr. 19, Pratt Sept. 4, Ethridge Dec. 24, Tippett June 9, James Mar. 28, Draver Mar. 29, Bernert Sept. 6, Bailey Nov. 19, Hansen Nov. 10, Yoss Aug. 13, Hagen Mar. 21, Johnson Apr. 20, Linn Apr. 25, 

